tsinghuamicroch36asymmetricinformation(清华李稻葵)

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1、ChapterThirty-SixAsymmetricInformationInformationinCompetitiveMarketsInpurelycompetitivemarketsallagentsarefullyinformedabouttradedcommoditiesandotheraspectsofthemarket.Whataboutmarketsformedicalservices,orinsurance,orusedcars?AsymmetricInformationinMarketsAdoctorknowsmore

2、aboutmedicalservicesthandoesthebuyer.Aninsurancebuyerknowsmoreabouthisriskinessthandoestheseller.Ausedcar’sownerknowsmoreaboutitthandoesapotentialbuyer.AsymmetricInformationinMarketsMarketswithonesideortheotherimperfectlyinformedaremarketswithimperfectinformation.Imperfect

3、lyinformedmarketswithonesidebetterinformedthantheotheraremarketswithasymmetricinformation.AsymmetricInformationinMarketsInwhatwayscanasymmetricinformationaffectthefunctioningofamarket?Fourapplicationswillbeconsidered:adverseselectionsignalingmoralhazardincentivescontractin

4、g.AdverseSelectionConsiderausedcarmarket.Twotypesofcars;“lemons”and“peaches”.Eachlemonsellerwillaccept$1,000;abuyerwillpayatmost$1,200.Eachpeachsellerwillaccept$2,000;abuyerwillpayatmost$2,400.AdverseSelectionIfeverybuyercantellapeachfromalemon,thenlemonssellforbetween$1,0

5、00and$1,200,andpeachessellforbetween$2,000and$2,400.Gains-to-tradearegeneratedwhenbuyersarewellinformed.AdverseSelectionSupposenobuyercantellapeachfromalemonbeforebuying.Whatisthemostabuyerwillpayforanycar?AdverseSelectionLetqbethefractionofpeaches.1-qisthefractionoflemons

6、.ExpectedvaluetoabuyerofanycarisatmostAdverseSelectionSupposeEV>$2000.Everysellercannegotiateapricebetween$2000and$EV(nomatterifthecarisalemonorapeach).Allsellersgainfrombeinginthemarket.AdverseSelectionSupposeEV<$2000.Apeachsellercannotnegotiateapriceabove$2000andwillexit

7、themarket.Soallbuyersknowthatremainingsellersownlemonsonly.Buyerswillpayatmost$1200andonlylemonsaresold.AdverseSelectionHence“toomany”lemons“crowdout”thepeachesfromthemarket.Gains-to-tradearereducedsincenopeachesaretraded.Thepresenceofthelemonsinflictsanexternalcostonbuyer

8、sandpeachowners.AdverseSelectionHowmanylemonscanbeinthemarketwithoutcrowdingoutthepeaches